Fluid ingress location in wells



May 6, 1952 D. slLvERMAN ETAL 2,595,610

FLUID INGRESS LOCATION IN WELLS water l Wafer M p ATTORNEY May 6, 1952 AD. slLvERMAN ETAL 2,595,610

FLUID INGRESS LOCATION IN WELLS Filed Deo. 50, 1949 5 Sheets-Sheet 2 43-imumuml- 4 Recf l FI g5 INVENTORS: Daniel Silverman BY Ralph E,HarllineATTORNEY Figj" May 6, 1952 D. slLvr-:RMAN ETAL 2,595,610

FLUID INGREss LOCATION IN wELLs ATTORN EY i and well equipment.

Patented May 6, 1952 UNITED STATES PATENT GFFICE FLUD INGRESS LOCATIONIN WELLS Application December 36, 1949, Serial No. 135,907

1'? Claims.

This invention relates to testing wells and is directed particularly todetermining the location oi ingress of well fluids, particularly inwells producing a plurality of such fluids, such as oil and gas wellswhich also produce water. As problems of duid-entry location arise mostfrequently in connection with oil and gas wells which produce undesiredwater or brine along with the desired hydrocarbon iiuids, the inventionwill be describe-d with reference to such wells, although its utility isclearly not of such limited extent.

UNumerous attempts have been made, and some commercial success has beenattained in solving problems of duid-entry location in oil and gaswells, but all of the methods heretofore employed have had their utilitysomewhat limited by certain difliculties and drawbacks. Almost all ofsuch methods have employed well-conditioning or preparation steps whichhave required extended periods of time and very careful manipulation ofthe well or of the conditioning fluids To avoid Iover-balancing thenatural uid pressures of the exposed well formations, thus forcing intothem foreign fluids which might later mask the identity of the trueformation iluids, extreme and often impractical precautions have beennecessary. Frequently, the success or the failure of a well-testingprocess has been dependent upon the manner of distribution of aparticular testing material through the well or the well fluids, suchmaterial being also more or less expensive and hazardous to handle inthe case of radioactive tracing agents and solutions. In addition, withsome testing methods, the significant indications are of such shortduration that theT could be completely missed, if the measuring ordetecting equipment happened to be at a different level in the well atthe critical time. In most of such prior art methods also, the tests arecarried out with the well under quite diierent producing conditionsAfrom those which may prevail during the normal production `of thedesired oil and gas from the well. Also a drawback in some cases is thefact that the in.-

sertion of additional tubing into the well, or more ground surface, witha minimum of interference with the normal producing of the well; (2) toprovide a conditioning procedure having no possibility of overbalancingthe static fluid pressures in the permeable formations and causingintrusion of foreign iiuids into them; (3) to employ inexpensive andnon-hazardous conditioning agents; (e) to produce in a well asemi-permanent indication or pattern which is capable of beingrepeatedly observed as long as or as often as desired, which pattern isreadily and simply interpretable; (5) to employ very simple testing andrecording equipment; (6) to carry out the testing with very little or nohandling or modifications ofthe well-producing equipment; (7) to obtainthe signicant indications with the well either at or close to theproducing equilibrium condition which prevails during normal fluidproduction; and (8) to control the producing conditions of the wellduring the testing steps at will from the surface. Other and furtherobjects, uses, and advantages of the invention will become apparent asthe description proceeds.

We accomplish the foregoing and other objects by a method of welltesting which involves, generally, first lowering and then in subsequentsteps mai-nt ining the bottom-hole pressure in the well below static,that is, below the bottom-hole pressure which exists when the well isshut in and all production has stopped; .placing a column ofconditioning liquid throughout the well test Zone, which ordinarilymeans replacing the formation fluids which accumulate there; flowing theconditicning liquid column through the test zone and past the producingformations, while formation iiuids enter and contaminate or dilute theconditioning liquid at their locations of ingress (due to thebelow-static bottom-hole pressure); and measuring the pattern ofcontamination as a function of depth.

By maintaining the bottom-hole pressure always below static, forexample, by pumping the well more or less continuously, at least twovery important advantages are gained: there is never any possibility ofintrusion of the conditioning liquidinto the well formations, and theformations are always producing their natural iiuids into the well bore.The testing is carried out with the formations producing at any desiredrate, even approaching that occurring during normal duid production.

There are` several ways of placing the conditioning liquid throughoutthe well test'zone, each having advantages in certain situations. It iseven possible toutilize `the well fluids themselves 3 after appropriateaddition of a conditioning agent which will be affected by the entry offurther Well fluids as the conditioned liquid ilows by the producingformations.

This will be better understood by reference to the accompanying drawingsforming a part of this application, taken with the following detaileddescription. In these drawings, in which the same reference numerals areapplied to the same or corresponding parts in the different figures:

Figures 1 to 4, inclusive, show in cross section a typical well and thefluid conditions therein before and during certain steps of theperformance of one modification of the testing process of our invention;

Figure 5 is a log of the fluid conductivity obtained as a function ofdepth in the well;

Figures 6 and 7 show the fluid conditions in a well during conditioningby the procedure forming a preferred embodiment of the invention; and

Figure 8 shows an embodiment of the invention utilizing treated welliluids as the conditioning liquid.

Referring now to these drawings, and to Figure l in particular, a Well Iis shown diagrammatically in cross section as equipped with a casing I Iand a tubing string I2 through which the well is produced from a pointnear the bottom by a conventional pump I3 operated, for example, by asucker rod string I4. If the inlet to pump I3 is not normally near thebottom of the well, or at least below the zone to be tested, it isplaced there prior to the beginning of the testing process of theinvention.

If well IU is shut in for a period of time so that a state ofequilibrium is reached, the well uids in the annulus I5 between casingII and tubing I2 rise to a top level I6, designated as the static fluidlevel, the fluid column then comprising an upper body II of oil and alower body I8 of salt water separated by a sharp interface I9.

When well I0 is in a state of producing or dynamic equilibrium, withfluid being removed by pump I3 through tubing I2, the fluid conditionsare as indicated by the dashed lines, with the top of oil I'I at theproducing fluid level 2l and the interface I9 between the oil I1 andsalt water I8 at the level 22 of the inlet to pump I3 where it is shownin Figure 2. The difference in bottom-hole pressure, between thecondition with the well fluids at the static level I6 on the one handand at the producing level 2l on the other hand, is that reduction inbottom-hole pressure required to cause the iiuids to flow from thesurrounding formations into the well at the rate determined by the rateof operation of pump I3 in lifting these fluids from the well IIJ. Forthe purposes of this invention, it is desirable but not essential toknow within approximate limits what these two pressures are, or at leastthe pressure diierence, as it is one of the important features of theinvention that all of the conditioning and testing steps are carriedwith the bottom-hole pressure below static-in other words, at a pressurelevel below that when the well is in static equilibrium, The proceduresto be described have proven useful in substantially all wells tested,but

ance with our invention, as much as possible of the oil body I7 isremoved'frorn the annulus I5 by producing or pumping it out through thetubing I2, while introducing fresh water 25 from a surface tank orsource 26 into the annulus I5 at a rate, determined by a control valve2l, which is a substantial fraction of but does not exceed the pumpingrate. If fresh water 25 is simply introduced alone into annulus I5 ontop of oil column II, the bottom-hole pressure having rst been reducedby pumping, a certain amount of mixing and overturning occurs, withglobules of water falling through the oil, due to the different speciiicgravities and the immiscibility of the two fluids.

This mixing of the oil and water does not ordinarily preventsatisfactorily conditioning the Well, however, since the rate of fallingof the water in globules through the oil I'I is low. Velocities of fallranging from four to ten feet per minute have been observed in a numberof wells. By continuing to pump while the water 25 moves slowly downwardin globules, a substantial portion of the oil column can be removed tomake space for the necessary conditioning water column to extend throughthe well test zone, without ever exceeding the static bottom-holepressure.

When it is desired, however, to minimize the intermixing of the oil Iland water 25, so as to displace the oil from the annulus I5 with thegreatest possible effectiveness, a deformable separating plug 29 ofpumpable viscous liquid or gel is interposed between the oil l? and thefollowing fresh water 25 to resist their tendency to mix and overturn.The plug 29 readily adapts itself to changes in shape of the annulus I5,passing tubing and casing joints and the like in a manner that wouldbeimpossible if it were a solid body rather than a highly deformableliquid or gel.

Suitable materials for forming plug 29 are, for example, a stiffemulsion of oil and water 3B or a wateror oil-base gel 3|. A suitableoil-base gel can be formed by adding a thickening agent such as Napalmto crude or relined oil, or a waterbase gel may comprise water plusbentonite or hydrolyzed starch. The separating plug material 29 maycomprise any of these materials, alone or in combination in the form oftwo or several layers. For example, it may be desirable to employ awater-in-oil emulsion 3i) in contact with the water 25 and'the oil-basegel 3| in contact with the oil I 'I to prevent contact of the water 25with the gel 3| which might cause breaking of the gel.

With the well in the condition shown in Figure 2, pump I3 is removingthe oil column and a minor amount of production from the well formationsthrough the tubing I2 to the surface, while water 25 is being introducedfrom supply 25 through valve 2 at a rate which is only slightly less`than the rate of pumping through the tubing measured on a weight basiswhich is the intended basis of measurement or comparison throughout areespecially useful in wells where the pressure this speciiication, unlessotherwise indicated.

' The introduction of the plug 29 and water 25 may be started just assoon as the bottom-hole pressure has been reduced below static bypumping. but it is preferably begun with the well near or at theproducing equilibrium level 2i. The im- -portant limitation is that therate of introduction of plug 29 and water 25 shall never exceed the rateof pumping of the well through tubing I2, so that as a result thebottom-hole pressure in well IG, after the initial reduction, never canreturn to or exceed the static Value. Consequently, none of the iiuidsin the annulus I5 can enter these ing lbeen produced through tubing l2,together with the gel 3l and the emulsion 3). A small amount of oil l1may still exist on top of the water column 25 due to some by-passing ofthe plug 29 and to the minor amount of oil produced by the wellformations during placement of the Water column 25 under the reducedbottom-hole pressure. Some globules il' of this produced oil are shownmoving upward through the water 2e in this figure. This oil maygenerally be disregarded, however, because subsequently introduced water25 readily falls past or through it to join the main water column, andits contribution to the bottom-hole pressure remains relativelyconstant.

The well l is now ready for the fluid measurement step of the processillustrated in Figure 4, to obtain the fluid conductivity log of Figure5.

lt will be assumed that the formations penetrated by well Hl produce oilover the two intervals 35 and 36 and salt water from the three zones.38, 39, and 4Q. A pair of fluid-conductivity electrodes 4| is loweredinto the annulus l5 on an insulated-conductor cable 42 carried on a reel43 at the surface at the top of well Il), suitable leads and slip ringsconnecting electrodes M throughY the cable on reel 43 to a currentsource M and an indicator or recorder 45.

Pump I3 is operated to lift fluids at a normal rate (norma is here usedin the sense that the pump stroke rate and length are the same as in theusual producing of well lil), or at any other preferred rate greater orless than normal, to draw down the column of Water 25 and simultaneouslyinduce oil and salt-Water production from the formations into the wellbore and water column 25. Additional water 25 from the surface supply 25is introduced at some fraction of the pumping rate, and this constitutesthe control of the well-formation producing rate. After any period ofsteady pumping and constant-rate water addition to annulus l5 from` thesurface, a producing equilibrium is reached where the rate of wateraddition plus the rate of fluid entry from the well formations equalsthe pumping rate. Thus by making the water addition rate large or small,the formation producing rate will be conversely small or large, and itis a simple matter to regulate it to any Value desired.

With the producing, pumping, and water introduction conditionsestablished, the rate of entry of salt water at each of Zones 3d, 39,and lli and the rate of downward movement of water 25 are constant, andthe pattern of contamination or dilution of the fluid column is a steadyor semipermanent one. It is only necessary to traverse the electrodesfil through the annulus I5 and record the fluid conductivity as afunction of depth on recorder d5 to obtain the log of Figure 5.

In this figure the topI of the main water column `produces theconductivity increase at 50, the saltwater stratum sii produces thegradual conductivity increase 5l, salt-water stratum 39 produce-s thesecond gradual increase 52, and the sudden increase to the final highvalue of conductivity 53 indicates the location of pump inlet level 22,below which there is almost always undiluted salt water. Since this saltwater generally cannot be displaced by fresh water 25, the existence ofthe bottom salt-water entry 4% is ascertained at the end of the drawdownby the build-up step in which pump I3 is stopped, and valve 21 isclosed. Well I0 continues to produce, raising the fluid level towardstatic, and the fluid entering from stratum 4E causes thehigh-conductivity indication 53 to appear to move upward,

as observed by the electrodes 4i, proving the` existence of the bottomfluid entry.

It is of course not necessary always to make the log of Figure 5 withthe well at any specic producing equilibrium, as the main features ofthe log and the zones of entry become apparent very early in thedrawdown, as the step of owing the conditioning water through the testzone is termed. Beginning with the bottom-hole pressure just understatic, if no water is added to annulus l5 While pump i3 is operatedsteadily, the well formations produce at an increasing rate, and watercolumn 25 flows downwardly at a decreasing rate, until the normalproducing equilibrium condition is reached. By repeatedly traversingelectrodes il through the iiuid column, logs are obtained of thecontamination pattern for a Whole series of different formationfluidproduction rates.

In steady-state testing only one traverse of electrodes lll is requiredto obtain the log of Figure 5. In actual practice, however, the'electrodes are traversed repeatedly until it is seen that a steady-statecondition has been reached by the fact that the log being obtained isrepeated. rShen the build-up step mentioned above to check bottom fluidproduction may be started.

In Figure 6 is illustrated another and preferred way of carrying out thetesting of our invention, Without the substantially complete preliminarydisplacing of the oil column illustrated in Figures 2 and 3. Thus thefresh water 25 from tank ZES is introduced at a steady rate which is asubstantial iraction, such as from 56% to '75%, of the well pump-ingrate, over a period of time while the well is pumped steadily by pump i3through tubing S2. This operation should continue at least until theirst water 25 introduced has fallen through the oil column il andreached the well bottom, as in this way the maximum amount of oil Il isdisplaced by the water. With a rate of fall between four and ten feetper minute and, say, a 3,000-foot column of oil, at least ve hours isrequired; and during this period the principal fluid lifted by the pumpifi is the oil il from the annulus fluid column, as production from theformations is held back by the increased bottomhole pressure of theadded water 25, This large amount of Water can be introduced and willultimately be available for testing purposes without the bottom-holepressure ever exceeding static.

The Water addition can be and preferably is Acontinued somewhat longerthan is required for it to reach bottom, in order to purge the well ofsalt accumulations which otherwise would initially contaminate the freshwater 25 and reduce its conductivity contrast with the well waterentering during the subsequent drawdown step.

A particularly advantageous way of carrying out this continuous wateraddition is to arrange for an interlocking control 55 between the tubingoutlet and the water inlet valve 2?, for example, by actuating a controlmechanism from a meter 55 through which the pump production passes, suchthat the water input rate is the desired predetermined fraction of thewell output. This water circulation step is then allowed to operatecontinuously, and unattended if desired, for several hours, preferablyovernight. If by chance the pump I3 stops, the interlocking control 55the descending fresh Water 25 by the formation water measured to producea log as in Figure but in order to avoid the interference of oilblanketing the electrodes it is preferred to stop the pumping and wateraddition temporarily and let the water form a consolidated columnextending at least through the well test zone,

This is shown in Figure '7, and when it is found by surveying withelectrodes il that the consolidated water column 25 is of suflicientheight to supply the contemplated drawdown, the pumping, and wateraddition if desired, are resumed. The contamination pattern presentlyappears, and a log with the indications 5|, 52, and 53 (Figure 5) isobtained by traversing the electrodes i up and down the well annulus.The control of the operation by water addition from the surface is thesame as was described in connection with Figure 4, and the sameprocedure of stopping pumping and water addition at the end of thedrawdown step to permit a build-up of fluids in the well annulus forindicating bottom fluid entry can be used.

In the event fresh water 25 is not conveniently available at the welllocation, the Well water itself, after addition of a suitable chemicalagent, can serve as the conditioning liquid. For example, by adding asmall amount of sulfuric acid to the well water and making electrodes 4Iof dissimilar metals a voltaic cell can be formed which is sensitivel todilution by entering Well water to vary the observed cell potential.

This can even be carried out entirely within the well as shown in Figure8. A long column of salt water I3 is built up through and above theproducing formations, either by addition from the surface through theannulus or by raising the level 22 of the inlet to pump I3 above theproducing formations and pumping olf the oil in the annulus fluid columnso that it is replaced by produced salt water.

The `pump inlet 22 is then lowered back to bottom and a conditioningagent such as sulfuric acid is distributed through the salt Water columnit by a bailer 6G which is traversed through the annulus. A preferredway of adding the conditioning agent, particularly if the salt-Watercolumn is long enough or is being added to from the surface, is tolocate the bailer 60 at a conditioning point just above the well testzone and add the agent to the salt water passing by this point duringthe drawdown and contamination survey.

By whatever way the well fluid column is treated, the resultant log ofcell potential as a function of depth, made while drawing down theconditioned salt Water past the producing formations and maintaining theproper bottom-hole pressure by fluid additions from the surface, is ofthe same general character as Figure 5 and has the same significance.The contamination or dilution pattern in the downwardly moving liquidcolumn has the same semi-permanence or stability as the pattern obtainedusing fresh water in the previous embodiments.

It should be noted that the invention, while so described, is notlimited solely to the detection of salt water, using fresh or treatedwell water as the conditioning liquid. There are wells, for example, inwhich the connate water resistivity is high enough that salt water is tobe preferred for the conditioning liquid, having a contrastingly lowerresistivity than the produced Well water. The indications obtained bysuch a variation in technique are, however, analogous to those obtainedas above described. It is also possible to locate the exact zones ofentry of other fluids in the well such as oil, by using as theconditioning liquid, not water or brine but a material miscible in thesame manner with oil as water is miscible with the well brine, butcontrasting with the oil in some measurable characteristic such asfluorescence, electrical conductivity, dielectric properties, opacity,and the like.

While our invention has thus been described by giving in detail thesequence of steps by which we arrive at the desired results, it will beapparent to those skilled in the art that certain modifications of thesesteps are possible without affecting the validity of the resultsobtained. The invention, therefore, should not be considered as limitedstrictly to the described procedure, but its scope is to be ascertainedfrom the appended claims.

We claim:

l. The method of testing a Well to determine locations of fluid ingresstherein which comprises the steps of placing a column of conditioningliquid throughout a producing zone to be tested in said well, flowingsaid column through said zone, and measuring as a function of depth aproperty of said conditioning liquid characterizing its contamination byformation fluids, all of said steps being carried out while maintainingthe bottom-hole pressure in said well below static, whereby intrusion orsaid conditioning liquid into the well formations is positivelyprevented and said formations are at all times producing their naturalfluids into the well bore.

2. The method of testing a Well to determine locations of fluid ingresstherein which comprises the steps of placing a column of conditioningliquid throughout and somewhat above a producingzone to be tested insaid well, pumping said well from a point near the bottom of said zoneto cause said column to move downwardly through said zone, and measuringas a function of depth a property of said conditioning liquidcharacterizing its contamination by formation fluids, all of said stepsbeing carried out while maintaining the bottom-hole pressure in saidwell below static, whereby intrusion of said conditioning liquid intothe well formations is positively prevented and said formations are atall times producing their natural fluids into the well bore.

3. The method of testing a Well to determine locations of fluid ingresstherein which comprises the steps of replacing a substantial portion ofthe fluid column in the well by a conditioning liquid which forms aconsolidated column extending at least through a test zone in said well,pumping said well to cause said consolidated column to move through saidtest zone, and measuring as a function of depth a property of saidconditioning liquid characterizing its contamination by formationfluids, all of said steps apodo-i6 being carried out while maintainingthe bottomhole pressure in said well below static, whereby intrusion ofsaid conditioning liquid into the wellI formations is positivelyprevented and said formations are at all times producing their naturalfluids into the well bore.

4. The method of testing a well to determine locations of fluid ingresstherein which cornprises the steps of replacing at least that portion ofthe fluid column in the well annulus extending through and substantiallyabove a producing zone to be tested with a conditioning liquid misciblewith the well fluid of which the ingress is to be located, pumping saidwell from a point below said zone to draw said conditioning liquiddownwardly through said zone, and measuring as a function of depth aproperty of said conditioning liquid characterizing its contamination byformation fluids, all of said steps being carried out while maintainingthe bottom-hole pressure in said well below static, whereby intrusion ofsaid conditioning liquid into the well formations positively preventedand said formations are at all times producing their natural fluids intothe well bore.

5. The method of testing a well to determine" locations of fluid ingresstherein which comprises the steps of continuously flowing anuncontaminated conditioning liquid from outside of a zone,

to be tested in said well through said zone, and measuring as a functionof depth a property of said conditioning liquid characterizing itscontamination by formation fluids, all of said steps being carried outwhile mantaining the bottomhole pressure in said well below static,whereby intrusion of said conditioning liquid into the well formationsis positively prevented and said formations are at all times producingtheir natural fluids into the well bore,

6. The method of testing a well to determine locations of fluid ingresstherein which comprises the steps of flowing a liquid past aconditioning point outside of a producing zone to be tested in saidwell, adding a conditioning agent to Said liquid at said point, thenflowing said liquid containing said agent through said zone, andmeasuring as a function of depth a property of said liquidcharacterizing the interaction of entering formation fluids and saidagent, all of said steps being carried out while maintaining thebottom-hole pressure in said well below static, whereby intrusion ofsaid conditioning liquid into the well formations is positivelyprevented and said formations are at all times producing their naturalfluids into the well b ore.

7. The method of testing a well to determine locations of fluidlngresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, introducing into the wellannulus on top of the fluid column therein a conditioning liquid at arate which is a substantial fraction of the well-pumping rate, andmeasuring as a function of depth a property of said conditioning liquidcharacterizing its contamination by formation fluids, all of said stepsbeing carried out while maintaining the bottom-hole pressure in saidwell below static, whereby intrustion of said conditioning liquid intothe well formations is positively prevented and said formations are atall times producing their natural fluids into the well bore.

3. The method of testing a well to determine locations of fluid ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, continuously introducingconditioning liquid into the well annulus at a rate which is asubstantial fraction of the pumping rate, until a condition of producingequilibrium is established in which said conditioning liquid flowsdownwardly past a producing zone in said well and the well formationsproduce into the well bore at a substantially constant rate,consolidating said downwardly flowing conditioning liquid into a columnextending at least through said zone, and measuring as a function ofdepth a property of said conditioning liquid characterizing itscontamination by formation fluids, all of said steps after the rst beingcarried out while maintaining the bottomhole pressure in said well belowstatic, whereby intrusion of said conditioning liquid into the wellformations is positively prevented and said formations are at all timesproducing their natural fluids into the well bore.

9. The method of testing a well to determine locations of fluid ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, introducing a conditioningliquid into the well annulus continuously over a period of time, atleast until said liquid reaches the well bottom, at a rate which is asubstantial fraction of the well-pumping rate, accumulating saidconditioning liquid into a consolidated column extending at leastthrough the well producing zone, and measuring as a function of depth aproperty of said conditioning liquid characterizing its contamination byentering formation fluids, while pumping said well to draw down saidcolumn through said zone and simultaneously produce formation fluidsinto said column at their locations of ingress.

l0. The method of testing a well to determine locations of fluid ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static,- introducing a deformableplug into the well annulus on top of the well fluids therein,introducing a conditioning liquid on top of said plug at a rate which isa substantial fraction of the well pumping rate, whereby a substantialportion of the formation uids in said annulus are removed from said wellby pumping, and said bottomhole pressure is maintained continuouslybelow static, drawing down said conditioning liquid as a consolidatedcolumn past the well producing zone while continuing said pumping tocause formation fluids to enter said column, and measuring as a functionof depth a property of said conditioning liquid characterizing itscontamination by said formation fluids at the locations of theiringress.

11. The method of testing a well to determine locations of water ingresstherein which comprises th'e steps of pumping said well to lower thebottom-hole pressure therein below static, continuously introducingconditioning water contrasting in electrical conductivity with the wellwater of which the ingress is to be located, into the well annulus at arate which is a substantial fraction of the pumping rate, until acondition of producing equilibrium is established in which saidconditioning water flows downwardly past a producing zone in said welland the well formations produce into the well bore at a substantiallyconstant rate, consolidating said conditioning water into a columnextending at least through said zone, drawing said column downwardlythrough said zone, and measuring as a function of depth the electricalconductivity of said conditioning water characterizing its contaminationby formation water, all of said steps after the first being carried outwhile maintaining the bottomhole pressure in said well below static,whereby intrusion of said conditioning water into the well formations ispositively prevented, and said formations are at all times producingtheir natural fluids into the well bore.

12. The method of testing a well to determine locations of water ingresstherein which cornprises the steps of pumping said well to lower thebottom-hole pressure therein below static, continuously introducingconditioning water contrasting in electrical conductivity with the wellwater into the well annulus, at a rate which is a substantial fractionof the well pumping rate, over a period of time substantially greaterthan that required for the first-introduced conditioning water to reachthe bottom of said well, whereby salt accumulations in said well arepurged by said conditioning Water, consolidating said downwardly flowingconditioning water into a column extending at least through the wellproducing zone, drawing down said column through said zone, andmeasuring as a function of depth the conductivity of said conditioningwater characterizing its contamination by formation water, all of saidsteps after the first being carried out while maintaining thebottom-hole pressure in said well below static, whereby intrusion ofsaid conditioning water into the well formations is positivelyprevented, and said formations are at all times producing their naturalfluids into the well bore. Y

13, The method of testing a well to determine locations of water ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, introducing into the wellannulus on top of the fluid column therein conditioning watercontrasting in electrical conductivity with the formation water, at arate which is a substantial fraction of the well-pumping rate,consolidating said conditioning water into a column extending at leastthrough a test zone in said well, drawing said column down through saidzone, and measuring repeatedly as a function of depth the conductivityof said conditioning water characterizing its contamination by formationwater, all of said steps after the rst being carried out whilemaintaining a bottom-hole pressure in said well below static, wherebyintrusion of said conditioning water into the well formations ispositively prevented, and said formations are at all times producingtheir natural fluids into the well bore.

14. The method of testing a well to determine locations of water ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, continuously introducingconditioning water contrasting'in electrical conductivity with theformation water into the well annulus at a rate which is a substantialfraction of the pumping rate, until a condition of producing equilibriumis established in which said conditioning water flows downwardly pastthe producing zone of said Well and the well formations produce into thewell bore at a substantially constant rate, consolidating saiddownwardly flowing conditioning water into a column extending at leastthrough said zone, drawing down said column through said zone, andmeasuring repeatedly as a function of depth the electrical conductivityof said conditioning water characterizing its contamination by formationwater while varying the rate of introduction of additional conditioningwater into the well annulus to vary inversely the producing rate of theformations into the well bore, all of said steps after the first beingcarried out while maintaining the bottom-hole pressure in said wellbelow static, whereby intrusion of said conditioning water into the wellformations is positively prevented, and said formations are at al1 timesproducing their natural fluids into the well bore.

15. The method of testing a Well to determine locations of water ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, introducing a deformable plugof viscous pumpable liquid into the well annulus on top of the oilcolumn therein, introducing on top of said plug conditioning watercontrasting in electrical conductivity with the formation water, at arate which is a substantial fraction of the well-pumping rate, whereby asubstantial portion of the oil column in said annulus is removed fromsaid well by pumping, and said bottom-hole pressure is maintainedcontinuously below static, drawing down said conditioning Water as aconsolidated column past the well producing zone while continuing saidpumping to cause formation fluids to enter'said column, and measuring asa function of depth the electrical conductivity of said conditioningwater characterizing its contamination by formation water entering saidcolumn at the locations of ingress.

16. The method of testing a well to determine locations of water ingresstherein which comprises the steps of pumping said well to lower thebottom-hole pressure therein below static, placing a substantiallycontinuous column of formation water containing a conditioning agentsensitive to dilution by additional formation water in the well borethroughout and somewhat above the producing zone to be tested in saidwell, flowing said column through said zone, and measuring in saidcolumn as a function of depth a property characterizing the eiect ofentering formation fluids on said conditioning agent, all of said stepsafter the first being carried out while maintaining the bottom-holepressure in said well below static, whereby intrusion of the conditionedformation water into the well formations is positively prevented, andsaid formations are at all times producing their natural fluids into thewell bore.

17. The method of testing a well to determine locations `of fresh wateringress therein which comprises the steps of pumping said well to lowerthe bottom-hole pressure below static, introducing into the wellannulus, on top of the liquid column therein, conditioning sal't'waterat a rate which is a substantial fraction of the well-pumping rate,until a condition of producing equilibrium occurs in which said saltwater flows downwardly past the producing zone in said well and the wellformations produce into the well bore at a substantially constant rate,consolidating said downwardly flowing salt water into a column extendingat least through said zone, drawing said column down through said zone,and measuring as a function of depth the conductivity of said salt watercharacterizing its contamination by entering fresh water from the wellformations, all of said steps after the first being carried out whilemaintaining the bottom-hole pressure in said Well below static, wherebyintrusion of said conditioning salt water into the well formations ispositively prevented, and said formations are at all times producingtheir natural fluids into the well bore.

` Number DANIEL SILVERMAN. 1,535,007 RALPH E. HARTIJNE. 1,537,919 W n 51,555,801 RET EMENCES CITED 1,786,196 The following refelences are ofrecord in the 1,865,847

le of this partent:

u 14 UNITED STATES PATENTS Name Date Huber Apr. 28, 1925 Elliott May 12,1925 Huber Sept. 29, 1925 Ennis Dec. 23, 1930 Ennis July 5, 1932

